Zeatin Riboside Content Research Articles

Photosynthesis, Chlorophyll Fluorescence, and Hormone Regulation in Tomato Exposed to Mechanical Wounding.

To understand the physiological responses of seedlings to mechanical wounding, we analyzed photosynthesis, chlorophyll fluorescence, and endogenous hormones in tomato (Solanum lycopersicum L.) subjected to varying levels of mechanical pressure. The results showed that, at 4 h after wounding, excess excitation energy was dissipated as thermal energy through the reduction in the photosystem II (PSII) opening degree and the increase in non-photochemical quenching. Photodamage was avoided, and stomatal closure was the most prominent factor in photosynthesis inhibition. However, 12 h after wounding, the photoprotective mechanism was insufficient to mitigate the excess excitation energy caused by the wound, leading to photochemical damage to physiological processes. Meanwhile, the non-stomatal factor became the most prominent limiting factor for photosynthesis at 80 N pressure. At 12 and 36 h after wounding, the concentrations of abscisic acid (ABA), methyl jasmonate (MeJA), indole-3-acetic acid (IAA), zeatin riboside (ZR), and gibberellic acid (GA3) in the stems showed a trend towards being increased, which promoted wound healing. However, after mechanical wounding, the ratio of stress- to growth-promoting hormones first increased and then decreased. This pattern can enhance stress resistance and promote cell division, respectively. Comprehensive analysis showed that the fluorescence parameter, photochemical quenching coefficient (Qp_Lss), was the most suitable indicator for evaluating mechanical wounding conditions.

Seed yield as a function of cytokinin-regulated gene expression in wild Kentucky bluegrass (Poa pratensis)

BackgroundKentucky bluegrass (Poa pratensis L.) panicle development is a coordinated process of cell proliferation and differentiation with distinctive phases and architectural changes that are pivotal to determine seed yield. Cytokinin (CK) is a key factor in determining seed yield that might underpin the second “Green Revolution”. However, whether there is a difference between endogenous CK content and seed yields of Kentucky bluegrass, and how CK-related genes are expressed to affect enzyme regulation and downstream seed yield in Kentucky bluegrass remains enigmatic.ResultsIn order to establish a potential link between CK regulation and seed yield, we dissected and characterized the Kentucky bluegrass young panicle, and determined the changes in nutrients, 6 types of endogenous CKs, and 16 genes involved in biosynthesis, activation, inactivation, re-activation and degradation of CKs during young panicle differentiation of Kentucky bluegrass. We found that high seed yield material had more meristems compared to low seed yield material. Additionally, it was found that seed-setting rate (SSR) and lipase activity at the stage of spikelet and floret primordium differentiation (S3), as well as 1000-grain weight (TGW) and zeatin-riboside (ZR) content at the stages of first bract primordium differentiation (S1) and branch primordium differentiation (S2) showed a significantly positive correlation in the two materials. And zeatin, ZR, dihydrozeatin riboside, isopentenyl adenosine and isopentenyl adenosine riboside contents were higher in seed high yield material than those in seed low yield material at S3 stage. Furthermore, the expressions of PpITP3, PpITP5, PpITP8 and PpLOG1 were positively correlated with seed yield, while the expressions of PpCKX2, PpCKX5 and PpCKX7 were negatively correlated with seed yield in Kentucky bluegrass.ConclusionsOverall, our study established a relationship between CK and seed yield in Kentucky bluegrass. Perhaps we can increase SSR and TGW by increasing lipase activity and ZR content. Of course, using modern gene editing techniques to manipulate CK related genes such as PpITP3/5/8, PpLOG1 and PpCKX2/5/7, will be a more direct and effective method in Kentucky bluegrass, which requires further trial validation.

Enhancing root physiology for increased yield in water-saving and drought-resistance rice with optimal irrigation and nitrogen.

Water-saving and drought-resistance rice (WDR) plays a vital role in the sustainable development of agriculture. Nevertheless, the impacts and processes of water and nitrogen on grain yield in WDR remain unclear. In this study, Hanyou 73 (WDR) and Hyou 518 (rice) were used as materials. Three kinds of nitrogen fertilizer application rate (NFAR) were set in the pot experiment, including no NFAR (nitrogen as urea applied at 0 g/pot), medium NFAR (nitrogen as urea applied at 15.6 g/pot), and high NFAR (nitrogen as urea applied at 31.2 g/pot). Two irrigation regimes, continuous flooding cultivation and water stress, were set under each NFAR. The relationships between root and shoot morphophysiology and grain yield in WDR were explored. The results demonstrated the following: 1) under the same irrigation regime, the grain yield of two varieties increased with the increase of NFAR. Under the same NFAR, the reduction of irrigation amount significantly reduced the grain yield in Hyou 518 (7.1%-15.1%) but had no substantial influence on the grain yield in Hanyou 73. 2) Under the same irrigation regime, increasing the NFAR could improve the root morphophysiology (root dry weight, root oxidation activity, root bleeding rate, root total absorbing surface area, root active absorbing surface area, and zeatin + zeatin riboside contents in roots) and aboveground physiological indexes (leaf photosynthetic rate, non-structural carbohydrate accumulation in stems, and nitrate reductase activity in leaves) in two varieties. Under the same NFAR, increasing the irrigation amount could significantly increase the above indexes in Hyou 518 (except root dry weight) but has little effect on Hanyou 73. 3) Analysis of correlations revealed that the grain yield of Hyou 518 and Hanyou 73 was basically positively correlated with aboveground physiology and root morphophysiology, respectively. The grain yield could be maintained by water stress under medium NFAR in WDR. The improvement of root morphophysiology is a major factor for high yield under the irrigation regime and NFAR treatments in WDR.

Nitrate stimulates adventitious rooting by increasing auxin content and regulating auxin- and root development-related genes expression in apple

Adventitious root (AR) formation is critical for cutting survival and nutrient absorption re-establishment. This complex genetic trait involves the interplay of nitrogen, endogenous hormones, and several key genes. In this study, we treated GL-3 apple (Malus domestica) in vitro shoots with nitrate and ammonium to determine their impact on AR formation, hormonal content, and gene expression patterns. Nitrate treatment significantly promotes adventitious rooting by increasing cell division, differentiation, and AR primordia formation compared to ammonium treatment. Elevated indole-3-acetic acid (IAA), reduced abscisic acid, and zeatin riboside concentrations were consistently observed with nitrate, likely crucial for promoting ARs over ammonium. Furthermore, Malus domestica auxin resistance1 (MdAUX1) expression was induced, increasing IAA levels. MdIAA23 was upregulated. Further results indicate that the higher expression levels of Malusdomestica WUSCHEL-relatedHomeobox gene 11 (MdWOX11), Malus domestica lateral organ boundariesdomaingene 16 (MdLBD16), and MdLBD29, and increased cell cycle-related gene expressions, contribute to auxin-stimulated adventitious rooting under nitrate conditions. In conclusion, this study establishes that auxin content and associated genes related to root development and cell cycle contribute to superior ARs in response to nitrate.

Agronomic and Physiological Performance of the Indica Rice Varieties Differing in Tolerance to Low Phosphorus

Phosphorus (P) deficiency and low P use efficiency (PUE) are limiting factors in rice (Oryza sativa L.) production. Understanding the agronomic and physiological traits of P-tolerant rice varieties is crucial for improving PUE. However, the agronomic and physiological traits of rice varieties differing in tolerance to low P have not been fully studied or comprehensively explored. Two varieties with strong tolerance to low P (STVs, low P tolerance index > 0.9) and two with weak tolerance to Low P (WTVs, low P tolerance index < 0.5) were grown hydroponically with normal P level (NP, 8.02 mg L−1) and low P level (LP, 0.401 mg L−1) in year 2020 and 2021. Results showed that, compared with NP, the LP significantly decreased grain yield, but enhanced P translocation efficiency (PTE), internal P use efficiency (IPE), and P harvest index (PHI) in all the varieties. The STVs showed better performance than the WTVs. Specifically, the STVs exhibited a 131.33% higher grain yield, 15.95% higher PTE, 41.6% higher IPE, and 8.84% higher PHI compared to the WTVs. The STVs also exhibited superior shoot traits, including increased productive tillers, leaf area index (LAI), leaf photosynthetic rate, shoot biomass, contents of indole-3-acetic acid (IAA) and zeatin (Z) and zeatin riboside (ZR) in leaves, non-structural carbohydrates (NSC) remobilization during grain filling, and content of NSC per spikelet, when compared to the WTVs under the LP treatment. Additionally, the STVs demonstrated better root traits, such as higher root biomass, root oxidative activity (ROA), root acid phosphatase (RAP) activity, and greater root IAA and Z + ZR contents. These shoot and root traits exhibited highly positive correlations with grain yield, PTE, and IPE. In conclusion, the STVs maintain higher grain yield and PUE under the LP treatment, due mainly to their improved root and shoot agronomic and physiological traits, which provide valuable references for selecting for P-efficient rice varieties.

Peculiarities of soybean-rhizobial systems subject to different levels of water supply fol-lowing treatment with succinic acid and epibrassinolide

All around the world, one of the leading – according to area of cultivated fields – oleic crops is soybean, which has a high demand for moisture. Given the significance of this crop and negative impact of drought on its yield, integrated research of the influence of insufficient water supply on the intensity of physiological-biochemical processes in those plants is necessary for identifying and understanding the drought-tolerance mechanisms of soybean, as well as symbiotic systems created with its participation, and also for search for ways to adapt it to this stressor. Therefore, our objective was determining the specifics of formation and functioning of the symbiotic systems of soybean and Bradyrhizobium japonicum, following treatment with succinic acid (0.01 g/L) and 24-epibrassinolide (0.00001 g/L), subject to different levels of watering. Our studies revealed that pre-sowing treatment of the seeds with a solution of 24-epibrassinolide with their subsequent inoculation with B. japonicum Т21-2 resulted in the most pronounced stimulation of formation and functioning of the symbiotic systems of soybean in the optimal growing conditions. At the same time, during water shortage, the intensity of nitrogen fixation was the highest in the plants grown from seeds that had been successively treated with the acid and the inoculant. We confirmed that water deficit led to significant increase in the overall content of phytohormones of cytokinin nature in the soybean root nodules, depending on the way the seeds were treated. However, the largest pool of cytokinins was seen in the plants that had been treated with succinic acid against the background of both optimal and insufficient water supply. Treatment of the seeds with 24-epibrassinolide caused significant excess of content of zeatin riboside over the content of zeatin during the flowering stage, whereas in the stage of pods formation it led to an opposite effect – excess of zeatin over zeatin riboside. Fourteen days-long water deficit decreased the content of chlorophylls in the leaves and grain productivity of the plants of all variants of the experiment. The use of growth regulators managed to alleviate the negative impact of stress and protect the pigment complex from ruination. Treatment of the seeds with solutions of succinic acid and 24-epibrassinolide provided the growth of soybean grain productivity regardless on water-supply level. The most efficient was 24-epibrassinolide. Therefore, use of 24-epibrassinolide for pre-sowing treatment of the soybean seeds provided formation of effective symbiotic systems with high nitrogen-fixing activity and caused a number of specific changes in the pattern of accumulation of free and complex forms of cytokinins in the root nodules of those plants. At the same time, the treatment provided the highest concentration of photosynthesis pigments in the soybean leaves, and as a result produced the greatest increase in grain productivity of plants of all the variants, regardless of levels of water supply. In turn, use of succinic acid produced the highest level of nitrogen-fixing activity in the case of the lowest number of root nodules in the conditions of insufficient water supply, and also caused significant accumulation of cytokinins in the nodules, compared with other studied variants against the background of both optimal and insufficient water supply. Therefore, it did result in increase in soybean grain productivity, but this was lower than in the plants treated with 24-epibrassinolide.

Impact of paclobutrazol on storage root number and yield of sweet potato (Ipomoea batatas L.)

Increasing storage root number is an important way to improve the yield of sweet potato. Here, two-year field experiments were conducted to study the effect of 0 (CK), 10, 20 and 30 mg kg−1 paclobutrazol (PBZ) on the phytohormones and lignin biosynthesis, and root growth and yield of sweet potato. The current study found that PBZ10 decreased the concentration of phytohormones gibberellin 3 (GA3), indole acetic acid (IAA) and abscisic acid (ABA) in the subterranean stem, whereas increased the concentration of zeatin riboside (ZR) and methyl jasmonate (MeJA), resulting in lower root length, volume and tip number at 3 and 5 days after planting (DAP). At 5 DAP, PBZ10 decreased GA3, MeJA and ABA concentration in adventitious root, and increased IAA and ZR concentrations, resulting in increased root length, volume, tip number and surface area at 10 DAP. By 5–30 DAP, PBZ10 decreased the concentration of GA3 and ABA in potential storage roots and increased the concentration of IAA, ZR and MeJA, thus increasing root number. At 10–20 DAP, PBZ10 decreased the lignin concentration in the potential storage root along with the expression of IbEXP1 and the enzymatic activities of phenylalanine ammonialyase, 4-coumaric acid CoA ligase and peroxidase, which are involved in the regulation of lignin biosynthesis, resulting in increased potential storage root diameter; interestingly, the opposite pattern was observed by 25–30 DAP. Then, PBZ10 increased the SR number at 40 DAP, and the yield of sweet potato at harvest time, and no PBZ was detected in SRs of PBZ10. But excessive concentration of PBZ is unfavorable to root development and led to a decrease of yield. These results indicated that a moderate PBZ (10 mg kg−1) application could reasonably regulate phytohormones and lignin biosynthesis, then increase storage root number and yield of sweet potato.

Optimizing Nitrogen Regime Improves Dry Matter and Nitrogen Accumulation during Grain Filling to Increase Rice Yield

Nitrogen (N) fertilizer is a critical element that affects rice yield. However, its effects on dry matter accumulation (DMA), N accumulation, and their physiological mechanisms with grain yield and N utilization efficiency still lack in-depth study. Three large-scale japonica rice varieties—Jinxiangyu 1, Nanjing 46, and Huaidao 5—were used in two field experiments with varying N fertilizer application rates to examine grain yield and N utilization efficiency. The results showed that: (1) In the range of 0~360 kg ha−1 total N application rate (TNAR), the rice yields of the three cultivars were maximum under the TNAR at 270 kg ha−1. The optimal TNAR for the highest yield of Jinxiangyu 1, Nanjing 46, and Huaidao 5 were calculated based on quadratic regressions with values of 305.5 kg ha−1, 307.6 kg ha−1, and 298.0 kg ha−1, and the corresponding yields were 10.3 t ha−1, 10.6 t ha−1 and 10.2 t ha−1, respectively. The N utilization efficiency decreased gradually with the increase in TNAR, and the recovery efficiency decreased from 35.7~38.19% to 29.61~31.59%. (2) The yield was significantly positively correlated with DMA and N accumulation from the heading stage (HD) to the maturity stage (MA). The DMA and N accumulation of HD-MA were significantly positively correlated with leaf photosynthetic rate, non-structural carbohydrate (NSC) accumulation in stems, root oxidation activity, zeatin (Z) + zeatin riboside (ZR) contents in roots, and nitrate reductase (NR) and glutamate synthase (GOGAT) activity in HD. (3) In the range of 0~216 kg ha−1 panicle N application rate (PNAR), the rice yield was maximum under the PNAR at 108 kg ha−1. The optimal PNAR for the highest yield of Jinxiangyu 1 was calculated based on the quadratic regression with values of 139.5 kg ha−1, and the highest yield was 9.72 t ha−1. The leaf photosynthetic rate, NSC accumulation in stems, root oxidation activity, Z + ZR contents in roots, and NR activity in leaves in rice were higher under 108 kg ha−1 PNAR. Excessive application of panicle fertilizer reduced the above physiological indicators and rice yield. The above results showed that optimizing N fertilizer could increase the leaf photosynthetic rate, NSC accumulation in stems, root oxidation activity, Z + ZR contents in roots, and NR activity from HD to MA, which was beneficial to improving DMA and N uptake during HD-MA, thus improving grain yield and N utilization efficiency in rice.

Biochemical Changes during Fruit and Seed Development in Nanjing Linden (Tilia miqueiana M.)

In China, the wild population of Nanjing Linden (Tilia miqueliana M.) is experiencing a drastic decline, primarily due to high levels of empty seeds. This study aimed to measure the biochemical and physiological changes during fruit and seed development in T. miqueliana to determine the developmental mechanism. The weight method and photosynthetic respiration were used to determine the biological aspects of both fruits and embryos, while transmission electron microscopy and the anthrone colorimetric method were used to determine the endosperm content, including sugar, starch, protein, and fat. Enzyme-linked immunosorbent assays were conducted to determine the levels of endogenous plant hormones such as indole-3-acetic acid (IAA), gibberellic acid 3 (GA3), zeatin riboside (ZR), and abscisic acid (ABA). The nonlinear least-squares method was used to fit the model of nutrient and hormone levels, revealing that fruit size expanded from the 5th to the 65th day and that fruit moisture content exhibited a downward trend, along with a decrease in fruit respiration intensity. Embryos were found to be fully developed between 35 DAF and 65 DAF, while the nutrients in the endosperm, i.e., sugar, starch, protein, and fat, continuously accumulated after 50 DAF. Additionally, ABA, IAA, GA3, and ZR contents were found to synergistically regulate seed development and maturation.

Combined application of organic fertilizer and chemical fertilizer alleviates the kernel position effect in summer maize by promoting post-silking nitrogen uptake and dry matter accumulation

Adjusting agronomic measures to alleviate the kernel position effect in maize is important for ensuring high yields. In order to clarify whether the combined application of organic fertilizer and chemical fertilizer (CAOFCF) can alleviate the kernel position effect of summer maize, field experiments were conducted during the 2019 and 2020 growing seasons, and five treatments were assessed: CF, 100% chemical fertilizer; OFCF1, 15% organic fertilizer+85% chemical fertilizer; OFCF2, 30% organic fertilizer+70% chemical fertilizer; OFCF3, 45% organic fertilizer+55% chemical fertilizer; and OFCF4, 60% organic fertilizer+40% chemical fertilizer. Compared with the CF treatment, the OFCF1 and OFCF2 treatments significantly alleviated the kernel position effect by increasing the weight ratio of inferior kernels to superior kernels and reducing the weight gap between the superior and inferior kernels. These effects were largely due to the improved filling and starch accumulation of inferior kernels. However, there were no obvious differences in the kernel position effect among plants treated with CF, OFCF3, or OFCF4 in most cases. Leaf area indexes, post-silking photosynthetic rates, and net assimilation rates were higher in plants treated with OFCF1 or OFCF2 than in those treated with CF, reflecting an enhanced photosynthetic capacity and improved post-silking dry matter accumulation (DMA) in the plants treated with OFCF1 or OFCF2. Compared with the CF treatment, the OFCF1 and OFCF2 treatments increased post-silking N uptake by 66.3 and 75.5%, respectively, which was the major factor driving post-silking photosynthetic capacity and DMA. Moreover, the increases in root DMA and zeatin riboside content observed following the OFCF1 and OFCF2 treatments resulted in reduced root senescence, which is associated with an increased post-silking N uptake. Analyses showed that post-silking N uptake, DMA, and grain yield in summer maize were negatively correlated with the kernel position effect. In conclusion, the combined application of 15–30% organic fertilizer and 70–85% chemical fertilizer alleviated the kernel position effect in summer maize by improving post-silking N uptake and DMA. These results provide new insights into how CAOFCF can be used to improve maize productivity.

Methyl jasmonate enhances salt stress tolerance associated with antioxidant and cytokinin alteration in perennial ryegrass

Jamonic acid (JA) and its derivatives such as methyl jasmonate (MJ) regulate stress tolerance but of the mechanism of MJ’s impact on turfgrass salt stress tolerance are not fully understood. The objectives of this experiment y was to investigate the responses of antioxidant and hormone metabolism to exogenous MJ in perennial ryegrass (<italic>Lolium perenne</italic> L<italic>.</italic>) subjected to salt stress. The MJ at 0, 25, 50, and 100 µM were applied to the ryegrass seedlings, and then the treated grass was exposed to salt stress at 250 mM NaCl. The grass plants serving as control were irrigated with regular water without MJ. Salt stress induced an increase in leaf electrolyte leakage (EL), and malondialdehyde (MDA) and reduction in turf visual quality rating and chlorophyll content. Exogenous MJ treatments suppressed EL and MDA, promoted chlorophyll content. The MJ treatments also improved superoxide dismutase (SOD) and catalase (CAT) and ascorbate peroxidase (APX) activity relative to salt treatment alone. Salt stress enhanced leaf gibberellin A4 (GA4) content but decreased indole-3-acetic acid (IAA), zeatin riboside (ZR), and isopentenyl adenosine (iPA). Exogenous MJ at 50 and 100 uM increased IAA, ZR, and iPA content under salt stress. Our data suggest that MJ treatment may enhance salt stress tolerance of perennial ryegrass by promoting the selected hormone level and antioxidant enzyme activity, and protecting cell membrane and photosynthetic function in perennial ryegrass.

Differences and mechanisms of post-anthesis dry matter accumulation in rice varieties with different yield levels

Post-anthesis dry matter accumulation (PDMA) plays an important role in yield, but the differences and mechanisms of PDMA among rice varieties with different yield levels are still unclear. Field experiments were conducted using six rice varieties with medium, high, and super high yield levels selected to not only analyze the relationship between PDMA and yield but also compare the physiological indexes among different varieties. The effects of grain fertilizer on PDMA and yield were also observed. PDMA and apparent transferred mass of non-structural carbohydrate (NSC) in stems from heading to maturity were significantly positively correlated with yield. The physiological indexes (root oxidation activity, zeatin ​+ ​zeatin riboside contents in roots and leaves, and leaf photosynthetic rate) at 0–20 days after anthesis (DAA) of super high-yielding varieties were significantly higher than those of medium-yielding and high-yielding varieties. In addition, the α-amylase activity in stems at 30–50 DAA of super high-yielding varieties was significantly higher than other varieties. Compared with no grain fertilizer application rate (GFAR), the GFAR for maximum yield and yield increase of super high-yielding varieties were higher than other varieties. The above physiological indexes at 10–20 DAA were increased under GFAR at 54 ​kg ​ha−1. The α-amylase activity at 30–50 DAA was inhibited under GFAR at 81 ​kg ​ha−1 that hindered NSC translocation, resulting in decreased yield. Our results indicated that higher PDMA and NSC translocation were the crucial characteristics that benefited the yield formation of super high-yielding rice varieties.

Response of Grain Yield and Water Use Efficiency to Irrigation Regimes during Mid-Season indica Rice Genotype Improvement

Understanding the performance of rice (Oryza sativa L.) agronomic traits and efficiency in water usage as well as grain yield under various irrigation regimes is crucial to achieving high resource use efficiency and high yield. In this study, 12 mid-season indica rice genotypes that have been grown in the lower reaches of the Yangtze River for the past 80 years were studied in a field experiment for two years under two irrigation regimes, i.e., conventional irrigation (CI) and alternate wetting and drying irrigation (AWD). The results showed that with genotype improvement in irrigation regimes, the total number of spikelets, shoot and root dry weight, root oxidation activity, total leaf area index (LAI), effective LAI, leaf photosynthetic rate, and abscisic acid contents and zeatin + zeatin riboside contents in root bleeding sap were significantly increased at main growth stages. AWD irrigation synchronously increased rice resource use efficiency (water use efficiency (WUE), radiation use efficiency (RUE), and temperature use efficiency (TUE)) and grain yield. Compared to CI, AWD more significantly enhanced the performances of rice genotypes in all studied traits. Based on our findings, a semi-dwarf hybrid rice genotype has great potential for high resource use efficiency and high yield under alternate wetting and drying irrigation, which was attributed to the improved agronomic characteristics and superior root traits.

The Application of Nitrogen Source in Regulating Lignin Biosynthesis, Storage Root Development and Yield of Sweet Potato

The understanding of the effects of nitrogen sources on lignin synthesis in sweet potato during storage root formation is limited. In this study, we investigated the effects of different nitrogen source on sweet potato storage root formation and development, as well as lignin synthesis in potential storage roots. The sweet potato cultivars Shangshu 19 and Jixu 23 were used in field experiments in 2019 and 2020. Three treatments were tested: (a) no nitrogen fertilizer application (control); (b) 60 kg hm−2 ammonium nitrogen; and (c) 60 kg hm−2 amide nitrogen. The results indicate that during sweet potato storage root formation, ammonium nitrogen significantly enhanced root activity compared to that of the control. The ammonium nitrogen treatment promoted IbEXP1 and inhibited Ibkn1 and Ibkn2 expression during the early stages of storage root formation, then increased gibberellic acid and decreased zeatin riboside content, enhanced phenylalanine ammonia lyase and peroxidase activities, and promoted lignin synthesis in potential storage roots. The opposite effects of ammonium nitrogen treatment on gene expression, hormone contents, and enzyme activity were observed in the late stages of storage root formation. Relative to the control, the ammonium nitrogen treatment significantly increased the number of storage roots during canopy closure. The ammonium nitrogen treatment produced the highest storage root yield and number of storage roots per plant. These results indicated that the ammonium nitrogen can inhibit root lignin synthesis, then promote storage root formation and increase the yield of sweet potato.

Differing responses of root morphology and physiology to nitrogen application rates and their relationships with grain yield in rice

Root morphology and physiology influence aboveground growth and yield formation in rice. However, root morphological and physiological differences among rice varieties with differing nitrogen (N) sensitivities and their relationship with grain yield are still unclear. In this study, rice varieties differing in N sensitivity over many years of experiments were used. A field experiment with multiple N rates (0, 90, 180, 270, and 360 kg ha−1) was conducted to elucidate the effects of N application on root morphology, root physiology, and grain yield. A pot experiment with root excision and exogenous application of 6-benzyladenine (6-BA) at heading stage was used to further verify the above effects. The findings revealed that (1) under the same N application rate, N-insensitive varieties (NIV) had relatively large root biomass (root dry weight, length, and number). Grain yield was associated with root biomass in NIV. The oxidation activity and zeatin (Z) + zeatin riboside (ZR) contents in roots obviously and positively correlated with grain yield in N-sensitive varieties (NSV), and accounted for its higher grain yield than that of NIV at lower N application rates (90 and 180 kg ha−1). (2) The root dry weight required for equal grain yield of NIV was greater than that of NSV. Excision of 1/10 and 1/8 of roots at heading stage had no discernible effect on the yield of Liangyoupeijiu (NIV), and it significantly reduced yield by 11.5% and 21.3% in Tianyouhuazhan (NSV), respectively, compared to the treatment without root excision. The decrease of filled kernels and grain weight after root excision was the primary cause for the yield reduction. Root excision and exogenous 6-BA application after root excision had little influence on the root activity of NIV. The oxidation activity and Z + ZR contents in roots of NSV decreased under root excision, and the increase in the proportion of excised roots aggravated these effects. The application of exogenous 6-BA increased the root activity of NSV and increased filled kernels and grain weight, thereby reducing yield loss after root excision. Thus, the root biomass of NIV was large, and there may be a phenomenon of “root growth redundancy.” Vigorous root activity was an essential feature of NSV. Selecting rice varieties with high root activity or increasing root activity by cultivation measures could lead to higher grain yield under lower N application rates.

Effects of rare-earth light conversion film on the growth and fruit quality of sweet pepper in a solar greenhouse.

Light is an important environmental factor influencing plant growth and development. However, artificial light supplement is difficult to spread for its high energy consumption. In recent years, rare-earth light conversion film (RPO) covering is being focused on to be a new technology to study the mechanism of light affecting plant growth and development. Compared with the polyolefin film (PO), the RPO film advanced the temperature and light environment inside the greenhouse. Ultimately, improved growth and higher yield were detected because of a higher photosynthesis, Rubisco activity and Rubisco small subunit transcription. Compared with that in the greenhouse with polyolefin film, the plant height, stem diameter and internode length of sweet pepper treated with RPO increased by 11.05, 16.96 and 25.27%, respectively. In addition, Gibberellic acid 3 (GA3), Indole-3-acetic acid (IAA), Zeatin Riboside contents were increased by 11.95, 2.84 and 16.19%, respectively, compared with that with PO film. The fruit quality was improved, and the contents of ascorbic acid (Vc), soluble protein and soluble sugar were significantly higher than those of PO film, respectively, increased by 14.29, 47.10 and 67.69%. On the basis of improved fruit quality, the yield of RPO treatment increased by 20.34% compared with PO film. This study introduces an effective and low-energy method to study the mechanism and advancing plant growth in fruit vegetables production.

Different miRNAs and hormones are involved in PEG-induced inhibition of adventitious root formation in apple

• PEG inhibited AR formation in GL-3 apple cuttings. • Lower IAA and higher ABA, JA-me, and ZR content lead to the inhibition of ARs. • 32 known miRNAs belonging to 22 families and 60 novel miRNAs were found to be differentially expressed. • A total of 81 target genes of known miRNAs and 62 targets of novel miRNAs were identified using degradome sequencing. In apples, adventitious root (AR) formation plays a crucial role in the life cycle, but drought stress limits this process. Multiple hormones and miRNAs play key roles in regulating ARs under drought conditions, but they are lacking in GL-3 apple clones. Therefore, to identify physiological and molecular changes behind the phenotype, GL-3 apple cuttings were treated with 6% polyethylene glycol (PEG) during the activation, induction, initiation, and emergence stages of AR formation and compared with a PEG-free control. Anatomical analysis indicates that 6% PEG treatment delays AR primordia formation and produces fewer thin ARs than control plants by decreasing the indole-3-acetic acid (IAA) endogenous content and promoting the abscisic acid (ABA), methyl jasmonate (JA-me), and zeatin riboside (ZR) content at all time points. Furthermore, 32 known miRNAs belonging to 22 families and 60 novel miRNAs were found to be differentially expressed. A total of 81 target genes of known miRNAs and 62 targets of novel miRNAs were identified using degradome sequencing. The known miRNA targets were classified into 50 GO terms. In biological processes, various terms related to the response to water deprivation; salt, heat, and cold stress; abscisic acid-activated signaling pathways; and so on, were observed. The KEGG analysis indicates 20 pathways from which plant hormone signal transduction, ribosomes, etc., were the most enriched. Further analyses indicated that miRNAs (miR167b, miR393g, and miR477a) related to IAA, ABA, and JA were induced; various stress-responsive miRNAs (miR171c, miR169o, miR159a, miR10979, and miR167a) were also promoted; and cell division and development-related miRNAs (miR396a and miR482a) were repressed by 6% PEG treatment. These results indicate that AR formation is an intricate biological process in apples under stressed conditions regulated by various hormones, related miRNAs, and target genes. This study delivers new information about the underlying regulatory mechanisms of AR formation in GL-3 and other plants.

STUDY ON in vitro INDUCTION OF ROOTING AND CHANGES IN ENDOGENOUS HORMONE CONTENT OF Lagerstroemia indica ‘ZIJINGLING’

Different media had different effects on the induction of rooting of Lagerstroemia indica ‘Zijingling’. The aims of this study were to identify the best rooting medium, determine the changes in endogenous hormone content in aseptic seedlings of ‘Zijingling’, and then analyze its role in the rooting process, to improve the rooting rate. Using a test tube seedling of ‘Zijingling’ as the experimental material, the tissue cells were observed via paraffin sectioning, and the changes in endogenous hormone content during the rooting process were determined using high-performance liquid chromatography. The results showed that 1/2 MS Medium had the most significant effect on rooting in the basic medium. The promoting effects of different auxins on rooting decreased in magnitude in the order 3-Indolebutyric acid (IBA) &gt; Naphthalene acetic acid (NAA)&gt; Indole-3-aceticacid (IAA). The optimal rooting medium was 1/2 MS + 0.6 mg L-1 IBA+ 15 g L-1 sucrose + 5 g L-1 agar + 200 mg L-1 activated carbon , and the highest induction rate of adventitious roots was 92.5%. The rooting of ‘Zijingling’ is classified as a primordial type of induced rooting. Exogenous IBA content promoted an increase in endogenous IAA and Gibberellic acid (GA3) contents. High contents of IAA, GA3, and Abscisic acid (ABA) and low content of Zeatin riboside (ZR) promoted the growth of adventitious roots, whereas high contents of IAA and ZR, and low contents of GA3 and ABA were required for the induction of root primordia. High levels of IAA/ZR and low levels of IAA/ABA promoted the differentiation of root primordia. However, low levels of IAA/ZR and high levels of IAA/ABA promoted adventitious root elongation.

DPC can inhibit cotton apical dominance and increase seed yield by affecting apical part structure and hormone content

The plant growth regulator mepiquat chloride (1,1-dimethylpiperidinium chloride, DPC) has been successfully used worldwide in cotton production. Fortified DPC (DPC+) can slightly damage young tissues of the epidermis, which has shown potential in cotton chemical topping in China. The underlying mechanism remains unclear. We investigated whether apical meristem and leaf morpho-physiological traits contribute to delayed growth of the main stem and increased seed yield in DPC or DPC+ as a chemical inhibitor. Two different DPC-sensitive varieties (Xinluzao 60, L60; Jinken 1402, JK1402) were field-grown using three different topping treatments manual topping (MT), no topping (NT) and chemical topping (DPC+ and DPC) in irrigated arid lands of Xinjiang for two years. The plant height decreased by 1.4–13.6% for the DPC+ and DPC treatments compared with the NT treatment and increased by 3.8 –9.2% compared with the MT treatment. The thickness of the leaves, palisade tissue (Pt) and spongy tissue (St) increased by 5.1–21.5% under DPC treatment compared with other treatments. The 3-indoleacetic acid (IAA) content of the leaves significantly increased by 25.0–93.8% at 10 days under the DPC treatment compared with that under the MT and NT treatments. The zeatin riboside (ZR) content of the leaves and apical buds increased up to 7.5 times at 40 days under the DPC+ and DPC treatments compared with that under the NT treatment. The accumulation of reproductive organ biomass and proportion of reproductive organ dry matter to total dry matter under the DPC+ and DPC treatments increased by 2.0–39.7% compared with that under the MT and NT treatments. The seed cotton yield between the DPC+ and DPC treatments showed no significant difference. However, the seed cotton yield of JK1402 under the DPC+ and DPC treatments significantly increased by 9.5–11.7% compared with that under the MT and NT treatments. The main stem length was significantly correlated with the stem length of the upper part and gibberellin (GA) content in the apical buds. The leaf Pt and ZR contents were significantly correlated with the boll weight and seed cotton yield. Collectively, the data suggest that improved morpho-physiological traits of the apical part, such as an increase in the IAA and GA contents in the apical buds, leaf Pt and ZR contents, and boll weight, inhibited growth of the main stem and increased seed cotton yield for DPC, which is cheaper than DPC+ as a chemical inhibitor under chemical regulation during the whole growth period.

Hormone and carbohydrate metabolism associated genes play important roles in rhizome bud full-year germination of Cephalostachyum pingbianense.

Cephalostachyum pingbianense is the only woody bamboo species that can produce bamboo shoots in four seasons under natural conditions. So far, the regulatory mechanism of shoot bud differentiation and development is unknown. In the present study, indole-3-acetic acid (IAA), zeatin riboside (ZR), gibberellin A3 (GA3 ) and abscisic acid (ABA) contents determination, RNA sequencing and differentially expressed gene analysis were performed on dormant rhizome bud (DR), growing rhizome bud (GR), and germinative bud (GB) in each season. The results showed that the contents of IAA and ZR increased while ABA content decreased, and GA3 content was stable during bud transition from dormancy to germination in each season. Moreover, rhizome bud germination was cooperatively regulated by multiple pathways such as carbohydrate metabolism, hormone signal transduction, cell wall biogenesis, temperature response, and water transport. The inferred hub genes among these candidates were identified by protein-protein interaction network analyses, most of which were involved in hormone and carbohydrate metabolism, such as HK and BGLU4 in spring, IDH and GH3 in winter, GPI and talA/talB in summer and autumn. It is speculated that dynamic phytohormone changes and differential expression of these genes promote the release of rhizome bud dormancy and contribute to the phenological characteristics of full-year shooting. Moreover, the rhizome buds of C. pingbianense may not suffer from ecodormancy in winter. These findings would help accumulate knowledge on shooting mechanisms in woody bamboos and provide a physiological insight into germplasm conservation and forest management of C. pingbianense.